Reset of human neocortical oscillations during a working memory task

Abstract

Both amplitude and phase of rhythmic slow-wave electroencephalographic activity are physiological correlates of learning and memory in rodents. In humans, oscillatory amplitude has been shown to correlate with memory; however, the role of oscillatory phase in human memory is unknown. We recorded intracranial electroencephalogram from human cortical and hippocampal areas while subjects performed a short-term recognition memory task. On each trial, a series of four list items was presented followed by a memory probe. We found agreement across trials of the phase of oscillations in the 7-to 16-Hz range after randomly timed stimulus events, evidence that these events either caused a phase shift in the underlying oscillation or initiated a new oscillation. Phase locking in this frequency range was not generally associated with increased poststimulus power, suggesting that stimulus events reset the phase of ongoing oscillations. Different stimulus classes selectively modulated this phase reset effect, with topographically distinct sets of recording sites exhibiting preferential reset to either probe items or to list items. These findings implicate the reset of brain oscillations in human working memory.

Potentiation of Gamma Oscillatory Activity through Repetitive Transcranial Magnetic Stimulation of the Dorsolateral Prefrontal Cortex

“…Although changes in oscillatory activity in the g-frequency band are most consistently observed, increases in the y-, a-, and b-frequency bands have also been associated with cognitive tasks (Gevins et al, 1997;Klimesch et al, 2001;Klimesch et al, 1997;Klimesch, 1999;Sarnthein et al, 1998;TallonBaudry et al, 1999;von Stein et al, 1999;Tesche and Karhu, 2000;Raghavachari et al, 2001;Jensen et al, 2002;Schack et al, 2002;Howard et al, 2003;Rizzuto et al, 2003;Gruber and Muller, 2005;Kaiser and Lutzenberger, 2005). In line with these studies, we found an increase in d-, y-, a-, and b-activity with WM load.…”

Oscillatory activity in the monkey hippocampus during visual exploration and memory formation

“…Our finding that hippocampal theta undergoes a phase reset with saccade onset is similar to the phase resetting observed in both rodent (28,29) and human (30,50,51) hippocampus with stimulus events during performance of memory tasks. This phase resetting has several important implications for memory formation.…”

Theta–gamma coordination between anterior cingulate and prefrontal cortex indexes correct attention shifts

“…5B), illustrating that the LFP theta-phase resets of the theta-gamma-correlated network also indexed whether attention shifts are successful. A plausible mechanism for such a farreaching consequence of phase-aligned theta activation can be found in recent studies that identified how a cue-induced phase reset effectively gates the outflow of a cortical circuit (35)(36)(37). These studies suggest that the phase reset-gated output of a local circuit can serve as the causal trigger of distant gamma activity phase locked to theta activity.…”

“…We thus correlated burst-LFP synchronization of neurons recorded at LFP recording sites that provided theta-phase or gamma-amplitude variations for theta-gamma correlations (SI Result S13). We found that burst synchronization to remote LFP gamma activity varied proportionally with the degree of theta-phase correlation with low-gamma amplitudes (35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50), an effect that was limited to those LFP sites that showed significant theta-gamma correlations (Spearman rank correlation r = 0.2, P = 0.044; Table S2 and SI Result S13). To our knowledge, these findings provide the first quantitative evidence that recording sites with LFP theta phases that engage in longrange gamma correlations also host neurons whose burst firing events synchronize long-range to gamma activity.…”